Chapter 12 Stoichiometry 12.2 Chemical Calculations 12.1 The Arithmetic of Equations 12.2 Chemical Calculations 12.3 Limiting Reagent and Percent Yield Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

What is the mass of 15 moles of copper? Flashback: What is the mass of 15 moles of copper? How many moles is 500 g of copper? What is the mass of 15 moles of Mg(OH)2? How many moles is 500 g of Mg(OH)2? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Balance: __Fe + __O2  __Fe2O3 Do Now: Balance: __Fe + __O2  __Fe2O3 How many moles of Fe2O3 will form from 8 moles of Fe? How many grams of Fe2O3 will form from 8 moles of Fe? How many grams of Fe2O3 will form from 100 grams of Fe? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Writing and Using Mole Ratios Moles Known Moles Unknown Using Mole Ratios Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Writing and Using Mole Ratios Steps for Solving a Mass-Mass Problem Grams Known Moles Known Moles Unknown Grams Unknown Using Molar Mass Using Mole Ratios Using Molar Mass Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Writing and Using Mole Ratios Mass-Mass Calculations N2(g) + 3H2(g)  2NH3(g) If I want to produce 150 grams of NH3, how many grams of hydrogen will I need? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Calculating the Mass of a Product Sample Problem 12.4 Calculating the Mass of a Product Calculate the grams of NH3 produced when 5.40 g of H2 reacts with excess N2. N2(g) + 3H2(g)  2NH3(g) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Change given unit to moles Sample Problem 12.4  2 mol NH3 3 mol H2 5.40 g H2  1 mol H2 2.0 g H2 17.0 g NH3 1 mol NH3 Given quantity Change given unit to moles Mole ratio Change moles to grams = 31 g NH3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Phosphorus burns in air to produce tetraphosphorus decoxide: 4P(s) + 5O2(g)  P4O10(s) What mass of phosphorus is needed to produce 3.25 mol of P4O10? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Phosphorus burns in air to produce tetraphosphorus decoxide: 4P(s) + 5O2(g)  P4O10(s) What mass of phosphorus is needed to produce 3.25 mol of P4O10? 3.25 mol P4O10   = 403 g P 31.0 g P 1 mol P 1 mol P4O10 4 mol P Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

How many grams of carbon dioxide is made when 100 grams of CH4 combusts with sufficient oxygen? CH4 + 2O2  CO2 + 2H2O Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

How many grams of carbon dioxide is made when 100 grams of CH4 combusts with sufficient oxygen? CH4 + 2O2  CO2 + 2H2O 44 g CO2 1 mol CO2 100 g CH4  16.0 g CH4 1 mol CH4  = 275 g CO2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

How many grams of Fe2O3 are produced when 12.0 grams of iron rusts? Do Now How many grams of Fe2O3 are produced when 12.0 grams of iron rusts? 4Fe + 3O2  2Fe2O3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

How many grams of Fe2O3 are produced when 12.0 grams of iron rusts? Do Now How many grams of Fe2O3 are produced when 12.0 grams of iron rusts? 4Fe + 3O2  2Fe2O3 159.8 g Fe2O3 1 mol Fe2O3 12.0 g Fe  55.9 g Fe 1 mol Fe  2 mol Fe2O3 4 mol Fe = 17.2 g Fe2O3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Other Stoichiometric Calculations The mole can be related to other quantities: 1 mol = 6.02 x 1023 particles 1 mol of a gas = 22.4 L at STP 1 mol 6.02x1023 particles and 1 mol 22.4 L and Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Other Stoichiometric Calculations The figure below summarizes the steps for a typical stoichiometric problem. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Calculating the Molecules of a Product Sample Problem 12.5 Calculating the Molecules of a Product How many molecules of oxygen are produced when 29.2 g of water is decomposed by electrolysis according to this balanced equation? 2H2O(l) 2H2(g) + O2(g) electricity Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

= 4.88  1023 molecules O2 Sample Problem 12.5 1 mol O2  2 mol H2O 29.2 g H2O  1 mol H2O 18.0 g H2O Given quantity Change to moles Mole ratio Change to molecules = 4.88  1023 molecules O2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Volume-Volume Stoichiometric Calculations Sample Problem 12.6 Volume-Volume Stoichiometric Calculations How many liters of nitrogen dioxide are produced when 34 L of oxygen react with an excess of nitrogen monoxide? Assume conditions are at STP. 2NO(g) + O2(g)  2NO2(g) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

34 L O2    1 mol O2 22.4 L O2 1 mol NO2 22.4 L NO2 2 mol NO2 Sample Problem 12.6 34 L O2    1 mol O2 22.4 L O2 1 mol NO2 22.4 L NO2 2 mol NO2 Given quantity Change to moles Mole ratio Change to liters = 68 L NO2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Finding the Volume of a Gas Needed for a Reaction Sample Problem 12.7 Finding the Volume of a Gas Needed for a Reaction Assuming STP, how many liters of oxygen are needed to produce 20.4 L SO3 according to this balanced equation? 2SO2(g) + O2(g)  2SO3(g) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Finding the Volume of a Gas Needed for a Reaction Sample Problem 12.7 Finding the Volume of a Gas Needed for a Reaction Assuming STP, how many liters of oxygen are needed to produce 20.4 L SO3 according to this balanced equation? 2SO2(g) + O2(g)  2SO3(g) 10.2 L O2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) Methane burns in air by the following reaction: CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) What volume of water vapor is produced at STP by burning 501 g of methane? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) Methane burns in air by the following reaction: CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) What volume of water vapor is produced at STP by burning 501 g of methane? 22.4 L H2O 1 mol H2O 501 g CH4  16.05 g CH4 1 mol CH4  2 mol H2O = 1.40  103 L H2O Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.